JPH045686B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for polymerizing 12-aminododecanoic acid, and more specifically, to polymerization of 12-aminododecanoic acid using powdered 12-aminododecanoic acid to improve physical properties such as color tone. The present invention relates to a method for polymerizing 12-aminododecanoic acid, which can smoothly and stably produce nylon-12 with an excellent high molecular weight.

(Prior Art and its Problems) Conventionally, a method for producing nylon-12 by polymerizing 12-aminododecanoic acid in a molten state is known. 12-Nylon is produced by polymerizing aminododecanoic acid.
In the case of 12, water is produced as a by-product due to the condensation reaction between the amino group and the carboxyl group. The polymerization reaction of 12-aminododecanoic acid is generally carried out in a molten state at a high temperature of about 180 to about 340°C, but since 12-aminododecanoic acid is in powder form at room temperature, the powder is poured from the top of the polymerization reaction tank. supplying 12-aminododecanoic acid in the form of
Continuously carried out industrially by molten in a polymerization reaction tank, allowing the polymerization reaction to proceed while flowing down the polymerization reaction tank, and taking out high molecular weight nylon-12 from the bottom of the polymerization reaction tank. It is. Therefore, water produced as a by-product during the polymerization reaction becomes gaseous and rises in the polymer melt liquid phase, collects in the gas phase at the top of the polymerization reaction tank, and is removed from the system from the top of the polymerization reaction tank. be done.

A powdered 12-aminododecanoic acid supply port is provided at the top of the polymerization reaction tank, and the powdered 12-aminododecanoic acid supplied from the supply port has a temperature lower than that inside the polymerization reaction tank. Therefore, the water vapor in the upper gas phase of the polymerization reaction tank is cooled near the 12-aminododecanoic acid supply port, causing dew condensation, and forming powder.
Wet the 12-aminododecanoic acid. The wet powdered 12-aminododecanoic acid adheres to the vessel wall near the 12-aminododecanoic acid supply port, and the amount of 12-aminododecanoic acid adhering to the vessel wall gradually increases while the continuous polymerization reaction continues. This increases until the supply port becomes blocked. As the powdered 12-aminododecanoic acid adheres to the vessel wall, the supply port becomes smaller, making it difficult to supply 12-aminododecanoic acid to the polymerization reaction tank at a constant rate. It becomes difficult to continuously produce homogeneous nylon 12-, and the continuous operation time must be shortened. Even if continuous operation is not stopped, the variation in the properties of the obtained nylon-12 increases, which is a serious drawback as an industrial method for polymerizing 12-aminododecanoic acid.

Therefore, in the industrial polymerization method of 12-aminododecanoic acid, it is necessary to smoothly supply powdered 12-aminododecanoic acid in a stable state for a long period of time.

A possible method for stably supplying powdered 12-aminododecanoic acid without narrowing or clogging the supply port is to supply 12-aminododecanoic acid accompanied by an inert gas. . This method makes it possible to stably supply powdered 12-aminododecanoic acid for a long period of time.

However, in the method of entraining an inert gas, oxygen from the air is also supplied to the polymerization tank together with powdered 12-aminododecanoic acid, and this oxygen mixes into the molten polymer, causing oxidative deterioration of the polymer. There are also problems in that the color tone and physical properties deteriorate.

By supplying powdered 12-aminododecanoic acid along with an inert gas, the oxygen that accompanies the 12-aminododecanoic acid is removed from the system to some extent, but this oxygen is almost completely removed. A large amount of inert gas is required for removal, and the amount of 12-aminododecanoic acid that is entrained in the inert gas and scattered out of the system is a non-negligible amount.

(Objective of the Invention) The present invention uses powdered 12-aminododecanoic acid as a raw material, and there is no blockage of the 12-aminododecanoic acid supply line, no scattering loss of 12-aminododecanoic acid, and a stable state. The object of the present invention is to provide a method for polymerizing 12-aminododecanoic acid, which can produce nylon-12 with excellent color tone and other physical properties.

(Structure of the Invention) As a result of researching the composition ratio, temperature, and state of a mixture of 12-aminododecanoic acid and water, the present inventors found that there is a correlation as shown in Figure 1. Ta.

In Figure 1, a mixture of 12-aminododecanoic acid and degassed water in any proportion is put into a glass tube, and the operations of reducing pressure and replacing with nitrogen gas are repeated to completely remove oxygen gas, and then nitrogen gas is removed. This is a correlation diagram of 12-aminododecanoic acid and water obtained by observing the changing state of the contents by placing the tube under normal pressure, sealing the glass tube, and gradually heating it in an oil bath. . In Figure 1, the "dissolved phase" indicates a uniform liquid state due to the mixture dissolving or melting, and the "solid phase" indicates that 12-aminododecanoic acid is in a solid state. , “slurry phase”
The mixture maintains a slurry state even after a long period of time.

In addition, the present inventors sealed a mixture of 10% and 20% by weight of 12-aminododecanoic acid with degassed water in a glass tube under a nitrogen gas atmosphere, and investigated the results in a dissolved phase state at various temperatures. The temperature was maintained for 4 hours, and the number average molecular weight (n) of the obtained polymer was measured. The relationship between the temperature and the number average molecular weight is shown in FIG. Second
As is clear from the figure, the higher the water content in the mixture, the lower the number average molecular weight of the resulting polymer.

The present invention was made based on such facts discovered by the present inventors, and the present invention consists of: (a) 100 parts by weight of 12-aminododecanoic acid and 2 to 2 to 10 parts of water;
By heating the mixture with 50 parts by weight to a temperature below 250°C at which a homogeneous liquid can be obtained under pressure, a homogeneous liquid whose main component is an oligomer of 12-aminododecanoic acid can be obtained. (b) prepolymerizing the liquid at a temperature of 130 to 250°C and a pressure of 3 to 20 Kg/cm ² (gauge pressure), then releasing the pressure to normal pressure, a step of preparing a prepolymer having an average molecular weight; and (c) polymerizing the prepolymer at a temperature of 130 to 250°C under normal pressure to reduced pressure while removing by-product water to obtain a prepolymer having a molecular weight of 14,000 or more. A method for polymerizing 12-aminododecanoic acid, comprising the steps of preparing nylon-12 having a number average molecular weight.

(Preferred Embodiments of the Invention) The polymerization method of the present invention will be explained with reference to the accompanying drawings.

FIG. 3 is a schematic cross-sectional view of an apparatus used to carry out one embodiment of the polymerization method of the present invention.

In FIG. 3, a dissolution tank 1 is provided with a stirrer 2, a 12-aminododecanoic acid supply port 3 and a water supply port 4 are provided at the top thereof, and an oligomer discharge port 5 is provided at the bottom thereof. , a heating jacket 6 is provided on its outer periphery. Polymerization tank 10
is provided with a stirrer 11, an oligomer supply pipe 12 is provided on the upper part of the stirrer 11, and the oligomer supply pipe 12 is connected to the oligomer outlet 5 via a valve 13. Furthermore, an inert gas supply port 14 is provided.
A nylon-12 exhaust port 16 is provided at the lower part of the exhaust port 15, and a heating jacket 17 is provided around the outer periphery of the exhaust port 15. Exhaust port 1
5 is fitted with an exhaust pipe 18 and connected to a vacuum pump (not shown) via condensers 19 and 19'. A gear pump 20 is attached to the nylon-12 outlet 16 to take out the nylon-12.

In step (a) of the present invention, powdered 12-aminododecanoic acid is supplied to the dissolution tank 1 from the 12-aminododecanoic acid supply port 3, and water, preferably sufficiently degassed and oxygenated, is supplied from the water supply port 4. Provide gas-free water. The ratio of 12-aminododecanoic acid to water is 12
- 2 to 50 parts by weight of water per 100 parts by weight of aminododecanoic acid
The proportion is 10 to 20 parts by weight, preferably 10 to 20 parts by weight.

After a predetermined amount of 12-aminododecanoic acid and water are charged into the dissolution tank 1, the dissolution tank 1 is sealed, and a heating medium is circulated through the heating jacket 6 to heat the contents mixture. The heating is carried out to a temperature range such that 12-aminododecanoic acid dissolves or melts and the mixture becomes a homogeneous liquid. The lower limit of this temperature range cannot be uniformly determined because it varies depending on the ratio of 12-aminododecanoic acid and water, as shown in Figure 1, but the heating described above can It is necessary to carry out the process over a range of temperatures. The upper limit is preferably 200°C or less, particularly about 180°C. This heating is performed under pressure, and the pressure is automatically determined by the amount and temperature of water in the dissolving tank 1.

The heating is preferably carried out while stirring the mixture, and is carried out until the mixture becomes a uniform liquid.

In step (a) above, when preparing a liquid in the dissolution tank 1, 12-aminododecanoic acid undergoes a polycondensation reaction to form an oligomer. Therefore, the above-mentioned liquid material is a mixture containing an oligomer of 12-aminododecanoic acid as a main component, and also contains a 12-aminododecanoic acid monomer and water. The degree of polymerization of the oligomer is generally about 2 to 6, and the number average molecular weight of the mixture is generally about 4,000 to 12,000.

If the amount of water relative to 12-aminododecanoic acid is more than the above range, the number average molecular weight of the oligomer will be small and the burden on the subsequent polymerization step will be large, and if the amount of water is less than the above range, The above liquid material is difficult to become uniform and has too high a viscosity.

The liquid material prepared in step (a) above is taken out from the oligomer outlet 5 and supplied to the polymerization tank 10 through the valve 13 and the oligomer supply pipe 12. A heating jacket 21 provided around the outer periphery of the valve 13 and the oligomer supply pipe 12 allows
The oligomers are not allowed to cool down.

In step (b) of the present invention, the above liquid material is heated at 130 to 250°C in the polymerization tank 10, preferably
A prepolymer having a number average molecular weight of 4000 to 12000 is prepared by prepolymerization at a temperature of 160 to 220° C. and a pressure of 3 to 20 Kg/cm ² (gauge pressure). If the polymerization temperature is lower than the above range, it is difficult for the polymerization reaction to proceed, and even if it is higher than the above range, the degree of polymerization will not increase further, leading to waste of energy and risk of thermal deterioration of the prepolymer.

In step (c) of the present invention, the polymerization tank 10
Relieve the pressure in the gas phase inside the tank and release it to normal pressure or exhaust port 1.
5 to 130 to 260°C, preferably 200 to 240°C, while maintaining a reduced pressure while evacuating with a vacuum pump.
The liquid polymer is further polymerized at a temperature of . In step (c), water produced as a by-product by the polymerization reaction of the polymer is removed from the system through the exhaust port 15. (c) In the step, a dry inert gas, such as nitrogen gas, is generally supplied from the inert gas supply port 14 at a rate of 0.5 to 3N.
By supplying at a supply rate of m ³ /hr, preferably 1 to 2 Nm ³ /hr, and exhausting the water together with the water through the exhaust port 15, by-product water can be removed even more effectively.

In the above steps (b) and (c), it is preferable to proceed with the polymerization reaction while stirring the liquid.
The stirrer 11 of the polymerization tank 10 may have any shape suitable for stirring a viscous liquid material other than the shape shown in FIG.

Further, in the above explanation, an example was shown in which the above steps (b) and (c) are carried out in the same polymerization tank, but they may be carried out using separate polymerization tanks.

In step (c) above, the polymerization reaction is carried out until nylon-12 having a number average molecular weight of 14,000 or more is obtained.

The resulting nylon-12 is removed from the nylon-12 outlet 16 by a gear pump 20.

Nylon-12 produced according to the present invention can be produced by using other types of polymerization tanks, for example, horizontal cylindrical polymerization tanks having a stirrer with a substantially horizontal stirring shaft, and by using water produced by-product during polymerization. It is also possible to polymerize under conditions such that nylon-12 is efficiently removed to obtain nylon-12, which has an even higher molecular weight.

(Effects of the Invention) According to the present invention, even if powdered 12-aminododecanoic acid is used as a raw material, the supply line will not be clogged, and there will be no loss due to scattering of 12-aminododecanoic acid. Furthermore, nylon-12 is produced stably and smoothly without oxygen being taken into the polymer during the polymerization reaction. Therefore, the present invention has the remarkable effect of being able to produce nylon-12 with excellent color tone and other physical properties in a stable state from powdered 12-aminododecanoic acid.

Example Using the apparatus shown in FIG. 3, 12-aminododecanoic acid was polymerized.

Pour 213 kg of degassed water into the dissolution tank 1 (inner volume: 3 m ³ ) from the water supply port 4, and while heating it by passing a heating medium through the heating jacket 6, add powdered 12-aminododecanoic acid from the water supply port 3. 850 kg of dodecanoic acid was charged and the dissolution tank was sealed.

When the content reached 160° C., the stirrer 2 was started to rotate, and stirring was continued for 1 hour while maintaining this temperature. The internal pressure of the dissolution tank was 6.8 Kg/cm ² G.
As a result, the contents of the dissolution tank become a uniform liquid, and the number average molecular weight calculated from the number of both end groups is
It was 350.

Next, the contents of the dissolution tank 1 were charged through the oligomer supply pipe 12 into the polymerization tank 10, which had been heated to 160° C. by passing a heating medium through the heating jacket 17.

While rotating the stirrer 11, the temperature of the liquid polymer was raised to 200°C, maintained at 200°C, and the by-produced water was removed from the system while maintaining the pressure inside the polymerization tank at 12 kg/cm ² G. Polymerize for 120 minutes, then gradually release the pressure to normal pressure over 45 minutes to reduce the number average molecular weight.
10000 prepolymers were prepared.

Next, while supplying dry nitrogen gas from the inert gas supply port 14 at a rate of 1 m ³ /hr, the temperature was reduced to normal pressure.
Polymerization was carried out at a temperature of 240°C for 2 hours with stirring, and 30 minutes after the stirrer 11 was stopped, the nylon-12 outlet 1
Nylon-12 was taken out from No.6.

The relative viscosity of the obtained nylon-12 was 2.42, the number average molecular weight was 24,000, and the number of terminal amino groups was 4.15×
10 ^-5 eq/g, number of terminal carboxyl groups is 4.17×
It was 10 ^-5 eq/g.

[Brief explanation of drawings]

Figure 1 is a 12-aminododecanoic acid-water relationship diagram showing the composition ratio and temperature of a mixture of 12-aminododecanoic acid and water, and Figure 2 is a 12-aminododecanoic acid-water relationship diagram. FIG. 2 is a diagram showing the relationship between polymerization temperature, number average molecular weight (n) of a polymer, and water content when a mixture of acid and water is subjected to closed polymerization in a dissolved phase state. FIG. 3 is a schematic cross-sectional view of an apparatus used to carry out one embodiment of the polymerization method of the present invention. 1 is a dissolution tank, 2 is a stirrer, 3 is a 12-aminododecanoic acid supply port, 4 is a water supply port, 5 is an oligomer discharge port, 6 is a heating jacket, 10 is a polymerization tank, 1
1 is a stirrer, 12 is an oligomer supply pipe, 14 is an inert gas supply port, 15 is an exhaust port, 16 is a nylon-12 discharge port, 17 is a heating jacket, 19,1
9' is a condenser, and 20 is a gear pump.

Claims (1)

[Scope of Claims] 1 (a) 100 parts by weight of 12-aminododecanoic acid and 2 parts of water
By heating the mixture with 50 parts by weight to a temperature below 250°C at which a homogeneous liquid can be obtained under pressure, a homogeneous liquid whose main component is an oligomer of 12-aminododecanoic acid can be obtained. (b) Prepolymerizing the liquid at a temperature of 130 to 250°C and a pressure of 3 to 20 Kg/cm ² (gauge pressure), then releasing the pressure to normal pressure, and a step of preparing a prepolymer having a number average molecular weight, and (c) polymerizing the prepolymer at a temperature of 130 to 250°C under normal pressure to reduced pressure while removing by-product water, to obtain a prepolymer having a number average molecular weight of 14,000 or more. A method for polymerizing 12-aminododecanoic acid, comprising the steps of: preparing nylon-12 having a number average molecular weight of .